It seems obvious now that smoking is bad for you. But, back in the first half of the last century, things were different. Medical textbooks were largely empty on the subject, and smoking was often seen as part of growing up.

How about a worldwide review of research in the field, pulled together and published by 40 epidemiologists for the WHO in June, that concluded that secondhand smoke increased the risk of lung cancer by 25%?

A lot, some of it salutary. In the 1920s, German scientists correctly picked up on x-rays as a possible source of genetic damage. In the same decade they also launched a huge campaign against tobacco, condemning it as a "plague" and "lung masturbation", according to Robert N Proctor, the historian, in his book The Nazi War on Cancer. The catch is that these scientists were eugenicists and were worried about the corruption of German germplasm. Smoking, for instance, was "unGerman" and a vice propagated by Jews.

The evidence that it can is growing. This week, Swedish researchers announced they had abandoned a trial to test the safety of hormone replacement therapy for women who had previously been treated for breast cancer.

Ben Goldacre: This scare started in 1999 with a circular email claiming that toxins were "purged" through perspiration, and that when the armpit sweat glands were blocked, toxins built up in the lymph nodes behind them, causing cancer in the upper outer quadrant of the breast.